1. Field of the Invention
The present invention relates to a shutter unit and to a camera capable of selecting a picture size and, more particularly, to a shutter unit used in a camera which can photograph in an ordinary picture size and in a picture size larger than that.
2. Description of the Related Art
As is well known, a camera capable of selecting a photographing picture size has already been proposed in, e.g., Published Examined Japanese Utility Model Application No. 44-8047 and Published Unexamined Japanese Patent Application Nos. 3-77930 and 3-77931. A camera of this type can photograph in a full-frame size and a half-frame size or 1/3 size evenly divided in the film feed direction by using a 35-mm width perforated JIS 135 model roll film.
The assignee of the present application also previously proposed a camera (Japanese Patent Application No. 3-205163) which could photograph in an ordinary photographing picture size (24 mm.times.mm) by using a 35-mm width perforated JIS 135 model roll film and in a photographing picture size larger than this size, e.g., in a picture size of 29 mm.times.41 mm, by using a 35-mm width non-perforated roll film which employed the same film cartridge as that of this perforated film.
In a camera capable of selecting a photographing picture size as described above, a photographing picture size selecting mechanism is required. When this mechanism is incorporated in the camera, the size of the camera is increased. Such an increase in size is not preferable since it is against the trend of size reduction.
Especially, when a photographing picture size selecting mechanism is to be incorporated in a single-lens reflex camera without changing the appearance of the camera, the space in the camera poses a problem. More specifically, a single-lens reflex camera has an arrangement as follows, as shown in FIG. 13, when its camera body 101 is seen from its front side. A pentaprism 102 is disposed in the upper central portion of the camera body 101. A mirror box 103, having a movable mirror 104 in it and a picture mask frame (aperture) 105 in its deep portion, is disposed below the pentaprism 102. A film supply chamber 107 for receiving a film cartridge 106 therein is disposed on the right side of the mirror box 103, and a shutter driving section 108 is disposed on the left side of the mirror box 103. A film winding chamber 109 having a film winding spool shaft is disposed on the left side of the shutter driving section 108. A shutter unit 110 (see FIG. 14), mounted on a shutter plate (to be described later) and having a vertical-run focal-plane shutter mechanism which is driven by the shutter driving section 108, is disposed between the picture mask frame 105 and the mirror box 103.
Accordingly, assuming that the horizontal sizes of the picture mask frame 105, the movable mirror 104, the mirror box 103, the film supply chamber 107, the space in which the opening/closing lock mechanism of the rear cover is to be disposed, the film winding chamber 109, and the outer casing wall are defined as A, B, C, D, E, F, and G, respectively, hardly no spare space exists in the horizontal direction. Although small spare spaces exist in 1 a horizontal size of the space in which the shutter driving section 108 is disposed and in 2 a space between the mirror box 103 and the film supply chamber 107, neither spaces can house the photographing picture size selecting mechanism.
When an extra space is to be reserved in the front-rear direction of the camera body 101 to dispose the photographing picture size selecting mechanism in it, since the photographing picture size selecting mechanism including picture size regulating members will be disposed immediately in front of the picture mask frame 105 and immediately behind the mirror box 103, the following inconveniences occur. That is, when the photographing picture size selecting mechanism is disposed in this position, the distance between the movable mirror 104 and the film surface in the direction of the optical axis is increased by the size of this mechanism in the front-rear direction. Thus, a screen 111 (see FIG. 14), which is disposed at a position where it is conjugate to the film surface with respect to the movable mirror 104, must also be moved upward. Then, the height of the camera is increased to increase the overall size of the camera, which is not preferable.